Figure 2

The one disadvantage of drip fertigation is the need for multiple applications of fertilizer. Ideally, crops should be fertilized no less than once a week, a routine that has yielded excellent results at the Noble Foundation. Plan on designating one day of the week as "feeding" day.

A fertigation schedule for 16 popular vegetable crops is given in Table 4 and was developed by researchers at the University of Florida for the commercial vegetable industry. We have modified it for garden use.

Note this about the schedule: it was designed to be used as a guide only. The fertilizer rates have been developed for crops grown on plastic-mulched raised beds composed of sandy soils low in organic matter. If a soil test-based pre-plant fertilizer application has been made or if the soil test indicates sufficient levels of all plant nutrients, the first two scheduled nitrogen applications may be omitted. Ammonium nitrate (34-0-0) is the most readily available form of soluble nitrogen. In the absence of a pre-plant fertilizer application, use a soluble form of a complete fertilizer such as Miracle-Gro 18-18-21, Rapid-Gro or Peter's.

When using this schedule on soils amended with large quantities of organic materials, expect to lower the scheduled rate according to (1) nitrogen content of the material (compost is an excellent source of nitrogen, while peat moss is a poor one); (2) stage of decomposition (nitrogen is more readily available from a well-decomposed source of organic matter, such as compost, than from raw animal manure or lawn clippings); and (3) soil temperature (as soil temperature increases, the rate of decomposition increases, thereby increasing the availability of nitrogen).

In certain situations in which organic soil amendments are used, little if any additional nitrogen will be required. Normally, several trials are needed to fine-tune this schedule to a particular practice. Regular soil testing, in combination with careful observation and note taking, will help you control nutrient management.